The present invention relates to a multimode Raman laser system, and in particular to a multimode Raman laser system suitable for generating high output parahydrogen Raman laser beam (16 .mu.m) to be used for molecular laser isotope separation for uranium enrichment.
In the past, the following method has been known as a method to generate high output parahydrogen Raman laser beam (16 .mu.m) to be used for molecular laser uranium enrichment method: As shown in FIG. 6, laser beam from transversely excited atmospheric pressure (TEA) CO.sub.2 laser system 1 comprising a stable resonator type oscillator is circularly polarized by a circularly polarizing element (not shown), and Raman conversion is performed by injecting the exciting laser beam 3, amplified to high output by multi-stage amplifier 2 called MOPA (Master Oscillator Power Amplifier), into Raman cell 4 filled with parahydrogen.
In the conventional system as described above, the exciting laser beam is obtained from TEA CO.sub.2 laser system 1 using stable resonator type oscillator, and it was disadvantageous in that conversion efficiency from input electric energy to light energy is low because loss occurs in the aperture of stable resonator type oscillator.
Also, because laser beam from TEA CO.sub.2 laser system 1 is used as circularly polarizing light required from Raman conversion and the circularly polarized element is low in strength, the laser beam emitted from TEA CO.sub.2 laser system must be passed through the circularly polarizing element at low output level. Therefore, the laser beam thus circularly polarized must be amplified by multi-stage amplifier (MOPA) before it is injected into Raman cell 4. Particularly, in case CO.sub.2 laser with weaker oscillation line (wavelength with lower gain such as 10R(32)) is used, the number of the amplifiers 2 must be extremely increased. This results in more complicated system and higher facility cost.
As described above, conventional type Raman laser system has been disadvantageous in that the conversion efficiency from input electric energy to light energy is low because loss occurs in the aperture in stable resonator type oscillator and that complicated system and expensive facility cost are required because multi-stage amplifiers are needed.